Thermionic valve circuits



y 1 29- P. w. WILLANS 1,712,060

THERMIONIC VALVE CIRCUITS Filed Feb. 2, 1 24 avwemto'a PETER W-WlLLA/VS.

saw, gu W 41 Patented May 7; 1929.

UNITED STATES OF CE;

PETER WILLIAM-WILLANS, or TOWCESTERENGLAND, Assienoa To ammo CORPORA-TION or AMERICA, A CORPORATION or DELAWARE.

THERMIONIC V LVE emeuimss Application filed man 2, 1924, Serial No.

' This invention relates to thermionic valve circuits and its object isto provide an arrangement in which it shall be impossible foroscillations that may be set up by a valve from being communicated toone of the cir-' cuits connected or coupled tothe valve, which circuitis hereinatter called the defended circuit.

In order that my invention may be more readily understood I will referto the accompanying drawings in which Figs. '1, 2 and 3 are diagrammaticillustrations of arrange ments embodying the inventions.

Figure 1 shows a wireless receiving system employing a valve V, the adustments of which may be such that it will oscillate for heterodynereception. Valve V is shown as having input electrodes 1 and 2 and aplate 3. The feedback is provided by a coil 4 in the plate circuit whichis magnetically coupled to a coil B in the grid circuit. The coil 13 isdivided at the point 5 intermediate its ends into two portions 6 and 7.In such acas e it is desirable' that oscillations thus generated by thevalve should be excluded from the aerial circuit 8 which includes avariable inductance A. for tuning it to the incoming signal. This iseliectcd accordingto the invention by dividing; the inductance B formingpart of the oscillatory circuit connected tothe grid and Figs. 1, 2 and3 the impedance X is equiva-'' lent to the combination of G plus theimpedance of the valve. In the specification and claims an impedanceequivalent to the valve is intended to include this combination as wellas its equivalents. This forms in effect a Vlheatstone bridge ofwhichthe two parts v i G and 7 of the inductance B are two arms and theimpedance X and thevalve the other two 690,223; and. in Great Britain nmes; 923.

a diagonal of thebridge. "Thus when a bal- "anceis obtained inthebridge, oscillations in B will not be transmittedlto the aerial; In thefour arnrlVheatstone bridge shown, points 5 and 9 constitutea pairotconjugate neutral points and theends 6 and 7 of coil B orany twopoints 'alongB having thesaine potential, constitute an opposite pair ofconjugate neutral points. i The frequency of os-c cillation of the valveV may be controlledby the: variable condenser F connected acrossthe'ends of coil B. l s

In place ofconnecting the aerial Ato a point in the inductance'B, I mayconnect it arms, while the aerial is connected to form toapointibetiveen two condensers which are '7 arrangedin series betweenthe grid of the valve the impedance X as shown in Fig. 2.

higure 3 shows a modified arrangement in which the oscillatory circuitcontaining theinductance B is connected to the grid 2? v throughtheupper part for .an additional inductanceC, the lower part 6 of which isconnected through'the impedance X a) the filament lot the valve V.Injthis case the impcdance'X consists of a valv i nilai"to the valve Vbut of course"unenergized: It the valve V is llfLlJlQ to pass gridcurrent the 'unenergized valve may he shunted across its grid andfilament by a balancing resistance C}; which th eretore forms part ofthe compensating impedance. The plate ot' theunenergized valve may beconnected to that of V in accordance with known practice in order to 1prevent potentials on'the anode from setting up currents in the aerial.

1 The aerial A is coupled to the coil electronia 'netically butisfscreened fromfit 'electrostatically an earth screen D.

Instead of the 'coil B being tuned the condenser F as shown the coil Emay be so tuned. c 1 I 1 i v I Havingicdescribed my invention what Iclaim is: i

charge valve regeneratively 7 connected, of a circuit associatedtherewith for mpressing 1. The combination with anelect-ronidis Isignals on the input electrodes of the valve, a divided impedance havingone end connected to the control electrode of said valve, and a circuitcomposed of two parallel branches, one comprising the input electrodesof the valve and a portion of the impedance, the other branch comprisingthe other port-ion of the impedance and a balancing impedance equivalentto the input impedance of the valve, said parallel branches being joinedat the filament of the valve and at the midpoint of the impedance andsaid first-mentioned circuit being symmetrically disposed with referenceto the two branches whereby the first-mentioned circuit is defended fromoscillations of the valve.

2. The combination with an electron discharge valve, of a circuitassociated therewith for impressing signals on the input electrodes oftthe valve, a divided impedance having one end connected to the controlelectrode of said valve, a circuit composed of two parallel branches,one comprising the input electrodes of the valve and a portion of theimpedance, the other branch comprising the other portion of theimpedance and a balancing impedance equivalent to the input impedance ofthe valve, said branches being joined at the cathode of the valve andthe midpoint of the impedance, and a tuning element between thejunctions of the branches.

3. The combination with an electron discharge valve regenerativelyconnected, of a circuit associated therewith for impressing signals onthe input circuit of the valve, a divided impedance having one endconnected to the control electrode of said valve, and a circuit composedof two parallel branches, one comprising the input electrodes of thevalve and a portion of the impedance, the other branch comprising theother portion of the impedance and a balancing impedance in the form ofan unenergized valve similar to the first-mentioned valve, said branchesbeing joined at the cathode of the valve and the mid-point of theimpedance and said firstmentioned circuit being symmetrically disposedwith reference to the two branches whereby the first-mentioned circuitis defended from oscillations of the valve.

4. The combination with an electron discharge valve, of a circuitassociated therewith having means for impressing signals on the inputcircuit of the valve, a divided inipedance having one end connected tothe control electrode of said valve, and a circuit composed of twoparallel branches, one comprising the input electrodes of the valve anda portion of the impedance, the other branch comprising the otherportionof the impedance and a balancing impedance, said branches being joinedat the cathode of the valve and the midpoint of the impedance, and meansfor coupling the output circuit of the valve to said divided impedance,said lirst-n'ientioned means being connected across the junctions of thebranches whereby the first-mentioned circuit is defended fromoscillations of the valve.

5. The combination with a vacuum tube, of means for regenerativelycoupling its input and output circuits, said means having associatedtherewith a divided impedance in said input circuit, and means, forpreventing any effects of said regenerative coupling on a portion ofsaid input circuit containing the divided impedance, comprising a pairof parallel circuits shunted around said portion, each of said parallelcircuits containing one portion of said divided in'ipedance and anadditional impedance, said additional impedances bearing the same'ratioto each other as the portions of said divided impedances in the parallelcircuits.

6. In signalling circuits the combination of a bridge circuit includingan electron tube having a plate and two input electrodes, said tubehaving input and output circuits with a feedback therebetween externalto the tube, the input electrodes of said tube being connected to pointson one of the arms of the bridge and a source of signals impressedacross a pair of conjugate points of said bridge circuit, saidfeedbaclrbeing impressed on an opposite pair oi conjugate points of saidbridge circuit.

7. A signalling circuit arrangement comprising in combination, a bridgecircuit including a three electrode vacuum tube, a divided inductanceand a balancing impedance, said divided inductance being connected atone end to the grid of said tube and said balancing impedance connectedbetween the other end of said inductance and the filament of the tube,the signal potential being impressed across a pair of conjugate pointsof the bridge and means for coupling the output of said vacuum tube tosaid divided in ductance.

8. A circuit system comprising in combination, an input circuit, anoutput circuit, a vacuum tube having a plate, grid and filament, acircuit comprised of a divided impedance and a second impedance seriallyconnected, the terminals of said circuit being connected respectively tosaid grid and filament whereby a closed mesh circuit is formed having aconjugate pair of neutral points, said input circuit being connectedacross said pair of conjugate points, and said plate being electricallycoupled to said mesh circuit and to said output circuit.

9. The combination with a valve having a control electrode and cathode,of an inductance connected to its control electrode, an impedanceconnected to an intermediate point of the inductance and to the cathode,and a balancing impedance connected between the end of the inductance,which is remote from the control electrode, and the point Where theimpedance is joined to the cathode.

10. In combination, a bridge circuit including an electron tube havingan anode control electrode and cathode and having aieedback between itsinput and output circuits, the control electrode and cathode of saidtube being connected to points on one 10 arm oi said bridge c1rcu1t andstud feedback being impressed across a pair of conjugate points on saidbridge circuit. a

11. In a combination, as defined in claim 9, said balancing impedancebeing an unenergizedvalve'similarto the first valve.

-12. Ina signaling circuit arrangement, as defined in claim 7 saidbalancing impedance being an unenergized tube similar to the first tube.

PETER WILLIAM WILLANS.

